脊髓分级压迫对大鼠脊髓诱发电位的影响

刺激麻醉大鼠一侧腓总神经,在同侧L_(3-4)硬膜外的背柱部位记录到脊髓诱发电位(SEP),由快三相峰电位A波,慢负波N_1,N_2及正波P组成。这些电位在2—4小时的空白对照观察中,保持稳定。在压强分级递增压迫L_(4-5)及其尾侧邻近节段过程中,A波潜伏期未见变化;A波和N波峰潜伏期随压强递增而延长;A波、N波和P波幅度随压强递增呈线性下降;在压强值增到225mmHg(X)时,N波和P波消失,A波残留并变成最后电位。压强达300mmHg并持续5分钟后去除压迫时,SEP各波幅度在15分钟内迅速恢复到一定程度,然后恢复变得缓慢;慢波幅度较快波幅度恢复明显;A波峰潜伏期与幅度同步的恢复,N波峰潜伏期落后于幅度的恢复,实验结果表明:脊髓对机械压迫敏感,脊髓功能减低与压强增高呈线性关系。

The Effect of Spinal Graded Compression Upon Spinal Evoked Potentials in the Rat

Spinal evoked potentials (SEP) epidurally recorded from the ipsilateral dorsal columns of L_3-4 in anaesthetized rats following stimulating the common peroneal nerve consisted of a fast triphasic spike potential, wave A; slow negative waves, N₁ and N₂; and a positive wave, P. These waves remained stable throughout the period of blank control up to 2-4 hours. In the course of graded compression at L_4-5 and neighbouring segments caudal to them, no alteration was seen in the latency of wave A; the peak latencies of waves A and N were prolonged as graded compression increa sed progressively; the amplitude of waves A, N and P linearly decreased with increasing intensity of pressure and when the compression intensity came up to 225 (X) mmHg, waves N and P disappeared, while wave A remained and became a final potential. After removal of the compression, which had lasted 5 minutes at the leval of 300 mmHg, the a mplitude of SEP recovered quickly in the first 15 minutes and then the recovering rate slowed; recovery of slow waves was better than that of fast wave; the wave A’s peak latency recovered synchronously with retrieval of its amplitude, whereas the restoration of the peak latency of wave N was slower than that of its amplitude. These results indicate that the spinal cord is sensitive to mechanical compression and the decrease in function of the spinal cord correlates linearly with the increase in intensity of the pressure.